Metabolism: Basic concepts and design

Question 1

Metabolism

Answer 1

Highly integrated network of chemical reactions. Energy transduction takes place through metabolism.

Question 2

Energy transduction

Answer 2

Cells extract energy from environment, use to convert simple molecules into cell components

Question 3

2 categories of metabolism

Answer 3

Catabolism - reactions that extract energy from fuels

Anabolism - reactions that use this energy for biosynthesis

Question 4

When can a reaction occur spontaneously?

Answer 4

If the change in free energy (^G) is negative

Question 5

A thermodynamically unfavourable reaction can be driven by…

Answer 5

a thermodynamically favourable one, which is often the hydrolysis of ATP

Question 6

Energy derived from catabolism

Answer 6

Is transformed into adenosine triphosphate (ATP)

Question 7

ATP hydrolysis

Answer 7

Exergonic. Energy released can be used to power cell processes (Motion, active transport, biosynthesis)

Question 8

Why is ATP an energy-rich molecule?

Answer 8

Because it contains 2 phosphoanhydride bonds

Question 9

ATP formation and oxidation of carbon fuels

Answer 9

These reactions are coupled, either directly or through formation of ion gradients (Photosynthetic organisms generate ion gradients using light).

Question 10

Why is ATP consumed?

Answer 10

To drive endergonic reactions and in signal-transduction processes.

Question 11

Extraction of energy from foodstuffs by aerobic organisms (1st stage)

Answer 11

Large molecules broken down into smaller ones, such as AA’s sugars and FA’s.

Question 12

Extraction of energy from foodstuffs by aerobic organisms (2nd stage)

Answer 12

Small molecules degraded to a few simple units, such as acetyl CoA, that have widespread roles in metabolism

Question 13

Extraction of energy from foodstuffs by aerobic organisms (3rd stage)

Answer 13

Citric acid cycle and oxidative phosphorylation, in which ATP is generated as electrons flow to O2, the main electron acceptor, and fuels are completely oxidized to CO2.

Question 14

Motifs in metabolism

Answer 14

A small number of recurring activated carriers, such as ATP, NADH and acetyl CoA, transfer activated groups in many metabolic pathways. Many activated carriers are derived from vitamins, small organic molecules required in diets of many higher organisms. Key reaction types are used repeatedly in metabolic pathways.

Question 15

NADPH (example of motif)

Answer 15

Carries 2 electrons at a high potential, provides reducing power for reductive biosynthesis of cell components.

Question 16

Regulation of metabolism

Answer 16

Amount of some critical enzymes controlled by regulation of the rate of synthesis and degradation. Also, catalytic activities of many enzymes regulated by allosteric interactions and covalent modifications. Also, movement of many substrates and subcellular compartments into cells is controlled.

Question 17

The energy charge, which depends on the relative amounts of ATP, ADP and AMP, plays a role in metabolic regulation

Answer 17

High energy charge - inhibits ATP-generating (catabolic) pathways. Stimulates ATP-utilizing (anabolic) pathways.